1. Field Of The Invention
The present invention relates to an automotive air conditioning system, and more particularly, to a control apparatus for controlling operation of an automotive air conditioning system which includes an externally controlled variable capacity type refrigerant compressor.
2. Description Of The Prior Art
Control apparatuses for controlling operation of an automotive air conditioning system which includes an externally controlled variable capacity type refrigerant compressor are well known in the art.
According to one conventional control apparatus, during the initial operation of an automotive air conditioning system including a variable capacity type refrigerant compressor, air temperature Te' immediately downstream from an evaporator is controlled as indicated by dashed lines in FIGS. 5 and 6. With reference to FIGS. 5 and 6, from a time t0 when operation of the air conditioning system is initiated to a time t1' when the temperature Te' drops to a certain value T3 which is slightly greater than a set temperature Tset, the control apparatus maintains a pressure control point in a suction chamber of the compressor at a minimum boundary value of 1.0 kg/cm.sup.2 G to thereby quickly drop temperature Te'. This is accomplished by the control apparatus by outputting an electric signal having a certain amperage Ip1 to an externally controlled variable capacity control mechanism of the compressor. Once the temperature Te' drops to value T3, the pressure control point in the compressor suction chamber is varied to cause temperature Te' to approach set temperature Tset. This is accomplished by the control apparatus by outputting another electric signal having an amperage determined by the proportional control action of the control apparatus. The proportional control action is initialized at amperage Ip1.
As a consequence of the operation of the above conventional automotive air conditioning system, during the initial operation of the system, the air temperature Te' immediately downstream from the evaporator overshoots the set temperature Tset by an amount which is significant enough to delay the time period required for temperature Te' to approach the set temperature Tset. Accordingly, the passenger compartment of the automobile cannot be adequately air conditioned during the initial operation of the automotive air conditioning system.